1. Field
The present disclosure relates generally to non-destructive inspection and, in particular, to performing non-destructive inspection on a layered structure. Still more particularly, the present disclosure relates to a method and apparatus for detecting material changes or other inconsistencies in a composite structure.
2. Background
In manufacturing aircraft, vehicles, and other structures, inspection of parts used to form these structures is often performed to determine whether the parts will have desired parameters for a desired performance of the part. Additionally, the structures and parts are inspected as part of normal maintenance when the aircraft, vehicles, and other structures are in use.
Non-destructive testing is commonly performed on these parts. Non-destructive testing is used to evaluate the properties of a part without altering the ability to use the part in service.
Ultrasound testing is a type of non-destructive testing. Ultrasound testing is often used to perform inspections on aircraft parts that include, or are comprised of, composite materials. Ultrasound testing involves transmitting sound waves through a test object, such as an aircraft part or structure.
Ultrasound testing is commonly performed using a transducer. The transducer is configured to send sound waves into a test object and detect a response to the sound waves. The response to these sound waves is analyzed to determine whether inconsistencies are present in the test object.
Aircraft, cars, medical devices, and even clothing are being designed and manufactured with greater and greater percentages of composite materials. For example, composite materials are used in aircraft to decrease the weight of the aircraft. This decreased weight improves performance features such as payload capacity and fuel efficiency. Further, composite materials provide longer service life for various components in an aircraft. Composite materials may also decrease the weight of other items such as artificial limbs, bicycles, cars, body armor, or other desirable products.
Composite materials may be tough, light-weight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in a polymer resin matrix. Resins used in composite materials may include thermoplastic or thermoset resins. The fibers may be unidirectional or may take the form of a woven cloth or fabric.
In manufacturing composite structures, layers of composite material are typically laid up on a tool. The layers may be comprised of fibers in sheets. These sheets may take the form of fabrics, tape, tows, or other suitable forms. In some cases, resin may be infused or preimpregnated into the sheets. These types of sheets are commonly referred to as prepreg. The different layers of prepreg may be laid up in different orientations, and different numbers of layers may be used depending on the performance requirements of the composite structure being manufactured.
Inconsistencies may be introduced to the composite structure during manufacturing or during use of the composite structure. Due to the regular spacing of the layers that make up the composite material, inspection of the composite material may be more difficult than desired for some locations or some types of inconsistencies.
Further, some inconsistencies may not be conventionally detectable using conventional non-destructive techniques. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.